<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script src="https://unpkg.com/vue@next"></script>
<div id="app">
    <div :style="{fontSize: fontSize + 'em'}">
        <blog-item v-for="item in blogs" :key="item.id" :title="item.title" @showbig="changeBig">

        </blog-item>
    </div>

</div>
<script>
    const vueOpt = {
        data() {
            return {
                blogs: [
                    {title: 'aaa', id: 1},
                    {title: 'bbb', id: 2}
                ],
                fontSize: 1
            }
        },
        methods: {
            changeBig(){
                this.fontSize += 0.1
            }
        }
    }

    const app = Vue.createApp(vueOpt);
    app.component('blog-item', {
        data() {
            return {}
        },
        props: ['title'],
        template: `
            <span>{{title}}</span>
            <button @click="$emit('showbig')">click Me</button>
            <br>
        `
    })


    app.mount('#app')
</script>
</body>
</html>
